Modelling the risk of noise-induced hearing loss among military pilots

Noise is a significant risk factor in aviation, especially in military aviation. Even though our earlier studies have shown that the risk of noise-induced hearing loss (NIHL) among military pilots is small and the monitoring of their hearing is effective, we still need to develop methods of assessing the risk of NIHL more effectively at both the general and individual levels. In addition, many other risk factors are considered to contribute to the development of hearing impairment. The novel NoiseScan data management system enables assessment of the risk of developing hearing impairment on the basis of known risk factors. This study investigates the risk of hearing impairment among Finnish Air Force pilots using reasonably accurate noise exposure data and other risk factors for hearing impairment. This risk is also compared with that of industrial workers, whose risk followed the ISO 1999 prediction. Hearing among Finnish military pilots turned out to be better than predicted by the ISO 1999 model. The industrial workers had a larger number of risk factors than the pilots. Owing to the small number of risk factors, the hearing of pilots corresponds to approximately the 80th percentile, being 9-13 dB better than the 50th percentile obtained with the industrial population.     

Influence of the solvent composition on the aerosol synthesis of pharmaceutical polymer nanoparticles

Crystallization of pindolol from the melt was studied by differential scanning calorimetry (DSC) and polarized light thermomicroscopy (PLTM) in order to discriminate the polymorphic forms obtained by this method. The crystallization process originates one exothermic signal localized in two different well-defined temperature ranges. Fusion gives rise to overlapped curves, which were analysed by peak-fitting. The polymorphs were identified as the clusters formed with the values obtained for T(peak) of the component curves. Three polymorphic forms were exhibited by pindolol crystallized from the melt. Commercial pindolol presents only two of these forms.     

Taichiquan acutely increases heart rate variability

A group of 15 elderly men and 14 young male students of physical education made twice a series of Taichiquan (TCQ) practices. Their electrocardiograms were recorded on tape-recorder and heart rates and heart rate variability (HRV) were calculated from digitized data. Here we report the results of recordings in supine positions before and after the first and second series of TCQ. Intervals between heart beats (RRIs) and their standard deviation (SDNN) increased in older men from recordings before the exercise to postexercise. In young subjects the SDNN and total variance (TV) of RRIs increased. HRV increases immediately after TCQ-exercise in young and old male healthy subjects. Whether these practices have permanent effects and effects in patients need controlled and prospective studies.     

Aqueous humour flow after a single oral dose of isosorbide-5-mononitrate in healthy volunteers

PURPOSE: To investigate whether a nitric oxide donor given as a single oral dose is able to modify aqueous humour flow in healthy volunteers. METHODS: Ten healthy volunteers participated in a randomized, double-masked and placebo-controlled cross-over study. Aqueous humour flow was assessed by fluorophotometry after intake of isosorbide-5-mononitrate (ISMN), 10 mg. Topical timolol maleate, which is known to reduce aqueous humour flow, was used as a positive control. Intraocular pressure (IOP) was measured by applanation tonometry and blood pressure was registered. RESULTS: The basal rate of aqueous humour flow did not change significantly after a single oral dose of ISMN. The aqueous humour flow in the timolol-treated eye was reduced as compared to the contralateral control eye (p = 0.002). Mean IOP 6 hours after placebo and ISMN intake did not differ significantly. Timolol lowered IOP by 4 mmHg (p < 0.001). ISMN did not lower systolic blood pressure, but diastolic blood pressure was reduced by 4 mmHg (p = 0.048). CONCLUSION: A single oral dose of 10 mg ISMN had no significant effect on aqueous humour flow in healthy volunteers.     

The effects of vasopressin on systemic and splanchnic hemodynamics and metabolism in endotoxin shock

We compared the effects of vasopressin and norepinephrine on systemic and splanchnic circulation and metabolism in endotoxin shock in pigs. Twenty-one pigs were randomized to endotoxin shock (Escherichia coli endotoxin infusion) (n = 6), endotoxin and vasopressin (VASO; n = 6), endotoxin and norepinephrine (NE; n = 6), and controls (n = 3). Endotoxin infusion was increased to induce hypotension, after which vasopressin or norepinephrine was started to keep systemic mean arterial blood pressure >70 mm Hg. Regional blood flows and arterial and regional lactate concentrations were measured. Tonometers with microdialysis capillaries were inserted into the stomach, jejunum, and colon. Systemic mean arterial blood pressure >70 mm Hg was achieved in the VASO and NE groups. Vasopressin decreased cardiac output, superior mesenteric artery, and portal vein blood flow, whereas hepatic arterial blood flow increased. Arterial lactate concentration increased from 2.0 mM (1.6-2.1 mM) to 4.7 mM (4.7-4.9 mM) (P = 0.007). Systemic and mesenteric oxygen delivery and consumption decreased and oxygen extraction increased in the VASO group. Vasopressin increased mucosal-arterial PCO(2) gradients in all three locations, whereas luminal lactate release occurred only in the jejunum. Animals in the NE group remained stable. Vasopressin reversed hypotension but decreased systemic and gut blood flow. This was associated with hyperlactatemia, signs of visceral dysoxia, and jejunal luminal lactate release. IMPLICATIONS: Although vasopressin induces vasoconstriction in visceral region, its effects on splanchnic circulation and metabolism during septic-endotoxin shock are still poorly characterized. We evaluated the metabolic and hemodynamic effects of vasopressin and norepinephrine within the splanchnic area in porcine endotoxin shock.     

Sound exposure among the Finnish National Opera personnel

The purpose of the study was to determine how and when the personnel of the Finnish National Opera are exposed to noise and whether exposure depends on musical selection of repertoire. Additionally, an evaluation of sound exposure level due to individual rehearsals was included. The measurements were done using individual noise dosimeters and fixed-point measurements. From the measurements, annual noise exposure in the Opera was evaluated. The conductors, dancers, and double bass players were exposed to levels below 85 decibels, A-weighted, dB(A), which is the national action level. The choir members were exposed to sound levels of 92 and 94 dB(A). Within the orchestra, the highest sound exposure levels were found among percussionists, 95 dB(A); flute/piccolo players, 95 dB(A); and brass players, 92-94 dB(A). Other sound exposure levels among orchestra members varied from 83 to 89 dB(A). Soloists and rehearsal pianists are likely to be exposed to sound levels exceeding the national action level. From an exposure perspective, the individual rehearsals, 79-100 dB(A), proved to be as important as performances and group rehearsals, 82-99 dB(A), among orchestra musicians and choir singers. The ambient sound level for the lighting crew was 76 +/- 4 dB(A). However, the measured sound levels at the ear varied from 77 to 92 dB(A) due to the communication via headphones that had individual volume control. For the majority of personnel of the Finnish National Opera, sound exposure level exceeded the national action level value of 85 dB(A). Artists exceeded the action level during both individual and group rehearsals, as well as during performances. Hearing protection has been designed for musicians. Education/reinforcement is required to ensure it is worn.     

Treatment improves serotonin transporter binding and reduces binge eating

Rationale Serotonin (5-HT) is involved in the control of eating behaviour by inhibiting food intake. Obese women with binge-eating disorder (OB-BED) were recently found to have reduced 5-HT transporter binding. Objectives The aim of this study was to investigate the effect of a successful treatment on 5-HT transporters in OB-BED. Methods The 5-HT transporter binding of seven OB-BED was measured by single-photon emission computed tomography (SPECT), by using iodine-123-labelled nor-β-CIT as a tracer, before treatment and after successful treatment, when the OB-BED were asymptomatic. Treatment consisted of group psychotherapy and fluoxetine medication. The control subjects, six obese women without eating disorders, were also studied twice by using SPECT. Results The 5-HT transporter binding of the symptomatically recovered OB-BED increased significantly (24±22%) after treatment, whereas in the control group, binding remained unchanged. Conclusions The results tentatively suggest that 5-HT transporter binding in OB-BED is an adaptive mechanism, which can be affected by treatment. Furthermore, there seems to be a link between improved 5-HT transporter binding and reduced binge eating.     

Comparison of the protective efficacy of neurotrophins and antioxidants for vibration-induced trauma

BACKGROUND: Patients undergoing temporal bone surgery or subjects working with vibrating tools may develop vibration-induced hearing loss (VHL). The aim of this study was to characterize the effects of pretreatment with N-acetylcysteine (NAC) or the neurotrophic factors, brain-derived neurotrophic factor (BDNF) and ciliary neurotrophic factor (CNTF), on VHL in an animal model. METHODS: Trauma to the cochlea was created with a vibrating probe placed on the bone of the external ear canal. BDNF and CNTF(Ax1) were delivered into the cochlea with mini-osmotic pumps. NAC was delivered into the cochlea by round window membrane (RWM) injection, by RWM permeation, or by oral administration. Hearing was evaluated with electrocochleography (ECoG). RESULTS: For control animals, vibration resulted in an average immediate threshold shift of 42 +/- 26 dB. NAC provided no protective benefit in animals subjected to VHL, regardless of the delivery method, with average threshold shifts varying from 38 to 56 dB across groups. NAC injection through the round window membrane was toxic, causing a ECoG threshold shift of >25 dB. In BDNF+CNTF(Ax1)-treated animals, immediate hearing loss was similar to that in control animals. There was a trend of threshold recovery by 1 day after vibration; however, the improvement was not statistically significant, nor was there a significant difference in 1-day thresholds across groups. CONCLUSIONS: Local infusion of BDNF and CNTF(Ax1) may enhance the rate of recovery from VHL, compared to control animals. In contrast, NAC had no effect on VHL, and when delivered by RWM injection, was actually toxic to the inner ear.     

Risk of Guillain-Barré syndrome after measles-mumps-rubella vaccination

OBJECTIVE: To assess the postulated causal association between measles-mumps-rubella (MMR) vaccination and Guillain-Barré syndrome (GBS). STUDY DESIGN: Active retrospective study based on linkage of the nationwide hospital discharge register with individual vaccination records. All patients hospitalized for treatment of GBS in Finland between November 1982 and December 1986 were included in the study. RESULTS: During the study period, 189 patients were hospitalized for treatment of GBS, and approximately 630,000 vaccine recipients received 900,000 doses of MMR vaccine; 24 of the 189 patients represented the prevailing target population for MMR vaccination, of whom 20 were vaccinated. MMR vaccination did not cause any increase over the background incidence of GBS, and no clustering of cases of GBS occurred at any time point after administration of MMR vaccine. The interval between vaccination and onset of symptoms of GBS exceeded the designated risk period of 6 weeks in all cases, varying from 80 days to years. MMR vaccination after recovery from GBS did not cause relapses of the illness. Respiratory or gastrointestinal tract infection predated the onset of GBS by 3 to 30 days in 20 (83%) of the 24 patients. CONCLUSIONS: No causal association seems to prevail between MMR vaccination and GBS.